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CentOS 6: default inbound traffic limited for CT's [message #45253] Mon, 20 February 2012 20:31 Go to next message
mojah is currently offline  mojah
Messages: 4
Registered: February 2012
Location: Belgium
Junior Member

From: *parallels.com
Hi,

I'm running OpenVZ on a CentOS 6 x64 machine with a stable kernel
(2.6.32-042stab049.6) and have even tried the issue below on the
test-branch (2.6.32-042stab052.2).
The issue I'm experiencing is also reported by Fredericep on the forum
but never got any follow-up:
http://forum.openvz.org/index.php?t=tree&goto=44238& &srch=inbound#msg_44
238

It's the exact same problem: my hardware node runs perfectly fine, it
has both full in- and outgoing networking speed. I can consistently
(3hours+ as tested) download files at my full line speed.
Whenever I try to same in a container, I can get a quick burst of
network traffic for a few seconds (10MB/s+) and then fall back to
10-200Kb/s, it varies.

My first troubleshooting went to incoming traffic shaping for the
eth0/venet0 interface, but that's not the case:
# tc -s qdisc ls dev eth0
qdisc mq 0: root
Sent 65350399 bytes 363366 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0

# tc qdisc del dev eth0 root
RTNETLINK answers: No such file or directory

But this is a default install and it doesn't have any traffic shaping
rules active. Neither does it have iptables active. It's all still
running the default OpenVZ stack.

Second idea was a possible hit of TCPSNDBUF or TCPRCVBUF as the defaults
(1720320) are rather low. But even changing it to something idiotic like
9223372036854775807 didn't make a difference. The /proc/user_beancounter
also didn't report any failed packets.

When tcpdumping the stream, I don't see anything abnormal except that
it's just slow traffic. Nothing out of the ordinary at first glance.

I'm looking for any advice on how to troubleshoot this, as I believe
this may very well be a CentOS 6 kernel bug - but to prove that, I would
of course need to dive deeper which is where my train of thought kind of
ends.

I look forward to any reply/idea this list may give me.

Mattias Geniar
Re: CentOS 6: default inbound traffic limited for CT's [message #45254 is a reply to message #45253] Tue, 21 February 2012 05:18 Go to previous messageGo to next message
Kirill Korotaev is currently offline  Kirill Korotaev
Messages: 137
Registered: January 2006
Senior Member
From: *parallels.com
Mattias,

1. The same doesn't happen on the very same host system (VE0)? Inside container only?
2. Are you using venet or bridged networking?

Thanks,
Kirill

On Feb 21, 2012, at 00:31 , Mattias Geniar wrote:

> Hi,
>
> I'm running OpenVZ on a CentOS 6 x64 machine with a stable kernel
> (2.6.32-042stab049.6) and have even tried the issue below on the
> test-branch (2.6.32-042stab052.2).
> The issue I'm experiencing is also reported by Fredericep on the forum
> but never got any follow-up:
> http://forum.openvz.org/index.php?t=tree&goto=44238& &srch=inbound#msg_44
> 238
>
> It's the exact same problem: my hardware node runs perfectly fine, it
> has both full in- and outgoing networking speed. I can consistently
> (3hours+ as tested) download files at my full line speed.
> Whenever I try to same in a container, I can get a quick burst of
> network traffic for a few seconds (10MB/s+) and then fall back to
> 10-200Kb/s, it varies.
>
> My first troubleshooting went to incoming traffic shaping for the
> eth0/venet0 interface, but that's not the case:
> # tc -s qdisc ls dev eth0
> qdisc mq 0: root
> Sent 65350399 bytes 363366 pkt (dropped 0, overlimits 0 requeues 0)
> rate 0bit 0pps backlog 0b 0p requeues 0
>
> # tc qdisc del dev eth0 root
> RTNETLINK answers: No such file or directory
>
> But this is a default install and it doesn't have any traffic shaping
> rules active. Neither does it have iptables active. It's all still
> running the default OpenVZ stack.
>
> Second idea was a possible hit of TCPSNDBUF or TCPRCVBUF as the defaults
> (1720320) are rather low. But even changing it to something idiotic like
> 9223372036854775807 didn't make a difference. The /proc/user_beancounter
> also didn't report any failed packets.
>
> When tcpdumping the stream, I don't see anything abnormal except that
> it's just slow traffic. Nothing out of the ordinary at first glance.
>
> I'm looking for any advice on how to troubleshoot this, as I believe
> this may very well be a CentOS 6 kernel bug - but to prove that, I would
> of course need to dive deeper which is where my train of thought kind of
> ends.
>
> I look forward to any reply/idea this list may give me.
>
> Mattias Geniar
>
RE: CentOS 6: default inbound traffic limited for CT's [message #45255 is a reply to message #45254] Tue, 21 February 2012 05:32 Go to previous message
mojah is currently offline  mojah
Messages: 4
Registered: February 2012
Location: Belgium
Junior Member

From: *parallels.com
> 1. The same doesn't happen on the very same host system (VE0)? Inside
> container only?

Indeed, host VE0 is unaffected, it has full network speed, only happens
inside containers. It happens on each new container I create, with basic
commands such as:

# vzctl create 5 --ostemplate centos-6-x86_64
# vzctl set 5 --ipadd x.x.x.x --nameserver y.y.y.y --hostname
valid-fqdn-hostname --onboot no --save
# vzctl start 5

> 2. Are you using venet or bridged networking?

Venet, which is the default if I'm not mistaken.

Regards,
Mattias
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